1. Field of the Invention
The present invention relates generally to a solar-powered vehicle, and more specifically to a solar-powered vehicle with multi-stage regenerative and mechanical braking.
2. Background
Transitioning away from petroleum-based energy sources has become a primary focus of research and development in the energy industry, as well as in industries that rely on petroleum fuels to power their products. Investment in alternative-fuel vehicles, for example, has skyrocketed in recent years.
In 2010 there were an estimated one billion vehicles in the world. The vast majority of these vehicles were gasoline-powered. Heavy reliance on petroleum-based fuels like gasoline presents a number of problems, and the major economies of the world are increasingly looking for ways to deal with, or prevent, these problems. Fossil fuel use has been identified as one of the largest contributors to air pollution around the globe. This pollution stems primarily from combustion of the fossil fuels, resulting in carbon monoxide, nitrogen oxide, hydrocarbon, and particulate emissions into the atmosphere. Carbon monoxide is highly toxic to air-breathing animals because of its interference with the ability of the blood to transport oxygen. Even small amounts of carbon monoxide can cause damage to cardiovascular tissue. Nitrogen oxides irritate the lungs and lead to acute respiratory disease, particularly in children. In addition to these direct harms, fossil fuel combustion is thought to be a major contributor to global climate change, resulting in innumerable indirect harms to humans and other species as temperatures around the globe increase. Use of petroleum fuels such as gasoline also results in evaporative emissions, which release fuel vapors into the atmosphere without combustion of the fuel.
Researchers looking into alternative fuel vehicles have explored a variety of options for moving vehicles away from a reliance on fossil fuels. These areas of research include battery/electric-powered vehicles, solar-powered vehicles, and vehicles powered by alternative fuels such as dimethyl ether (DME), ammonia, ethanol, biodiesel, biogas, hydrogen, and others. Each of these possible alternatives presents a variety of challenges and difficulties that must be overcome.
Solar-powered vehicles are known in the art. Such vehicles typically employ photovoltaic cells to convert energy from the sun into electric energy. Such vehicles have been largely impractical for day-to-day transportation. There are a number of factors that account for this impracticality. For example, power from a solar array is limited by the size of the photovoltaic array and the surface area of the photovoltaic array that is exposed to sunlight. This is, in turn, limited by the size of the vehicle itself. A larger vehicle, having more available space for photovoltaic cells, also requires more energy to move. Further, while batteries can be employed to store energy from the photovoltaic cells, the battery also adds to the overall weight of the vehicle. Photovoltaic panels are also heavy. In order to be useful, the energy supplied by a photovoltaic panel must be sufficient to offset the increased weight of the vehicle as a result of the panel.
Electric vehicles, such as solar-powered vehicles, can use regenerative braking to recapture, in useful form, some of the kinetic energy of the vehicle while slowing the vehicle. Regenerative braking is known in the art, and the energy obtained from such braking can be stored and used to provide power to the vehicle when necessary. Regenerative braking alone, however, is not sufficient to meet the braking needs of a vehicle. More traditional mechanical braking, such as dissipative braking, is also desired so that the operator of a vehicle can stop rapidly if required. Dissipative braking converts the kinetic energy of the vehicle into dissipative energy. Common examples of dissipative braking include disk brakes and drum brakes.
Control of two separate braking systems can provide a complex problem for the operator of a vehicle. In many vehicles, such as cars, computer systems control the interplay between the two braking systems, thereby reducing the burden on the operator of the vehicle. In simpler vehicles, where computerized control of braking systems is not desirable, control of the braking systems is left to the operator, who may have to rely on two separate mechanisms to control the individual braking systems. This adds a layer of complexity to the user's operation of the vehicle, and increases the risk of error on the part of the user.
What is needed, then, is a solar-powered vehicle that overcomes limitations in the art, providing a practical vehicle for day-to-day transportation. Also needed is such a vehicle wherein the regenerative and dissipative braking systems are easily controlled by the operator of the vehicle.